The effect of graphite number per area on tribological behavior of high-strength compacted cast irons in lubricated tests
Compacted graphite irons (CGIs) are considered a suitable option for heavy-duty engine blocks against grey cast irons due to their superior mechanical, thermomechanical, and tribological properties. Even though a large number of studies exist, high-strength CGIs still need more investigations related to the correlation between their microstructure and tribological performance. This study aims to investigate the effect of graphite number per area on friction and wear of two CGI grades - GJV450 and GJV500 - under lubricated ring-on-cylinder tests. The lubricant used was SAE CF-30 at 40 °C and the load was 75 N. Roughness measurements, scanning electron microscope, and electron dispersive spectrometry was performed to identify the differences in tribological behavior. The wear performance was evaluated using the variation on structure height S3k (=Spk+Sk+Svk). Any difference was determined for both cast irons in terms of coefficient of friction but the GJV450 presented a more intense plastic deformation, resulting in a higher variation of the S3k factor. Therefore, the reduction in graphite number per area affected the wear performance, justifying the preferential use of GJV500.
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